This invention relates to bistable deflection and, more particularly, to bistable deflection utilizing the parallel variable grating mode domain formation in thin layers of nematic liquid crystalline materials having negative dielectric anisotropy.
Liquid crystal diffraction gratings are known. See, for example, Carroll, Journal of Applied Physics, 43, 3 (1972); Greubel and Wolff, Applied Physics Letter, 19, 213 (1971). Variable grating mode domains in nematic liquid crystalline materials as distinguished from the Williams domains were denoted as such by Penz and Ford, Physical Review A, 6, 414 (1972) and studied by Greubel and Wolff. The Greubel and Wolff studies showed that the domains in the variable grating mode were formed in a direction perpendicular to the initial homogeneous alignment of the nematic liquid crystalline material. This alignment is hereinafter referred to as the perpendicular variable grating mode.
U.S. Pat. Nos. 3,758,195 and 3,813,145 to Hedman et al are directed to information display apparatus utilizing as a diffraction grating a cell containing a liquid crystalline material. It is believed that, at least in some instances, the diffraction results reported in these patents inherently resulted from a variable grating mode nematic liquid crystalline material having negative dielectric anisotropy and that, in some instances, the long axes of the domains in the variable grating mode were parallel to the initial homogeneous alignment (hereinafter referred to as parallel variable grating mode) rather than perpendicular as reported in the Greubel and Wolff article.
In new and growing areas of technology such as liquid crystal technology, new methods, apparatus, compositions, and articles of manufacture are often discovered for the application of the new technology in a new mode. The present invention relates to a novel bistable deflection system utilizing the parallel variable grating mode in nematic liquid crystalline materials.